Fuel injection pump for combustion engines



Nov. 27, 1951 PlELSTlCK $576,263

FUEL INJECTION PUMP FOR COMBUSTION ENGINES Filed Feb. a. 1950 mvs N TO A GUSTAV P/ELST/CK ATTORNE Y5 Patented Nov. 27, 1951 Gustav Pielstick, Saint Germain en Laye, France Application February 8, 1950, Serial No. 143,033 In France February 15, 1949 7 Claims.

This invention relates to the injection of fuel into combustion engines, more especially combustion engines operating under a high mean pressure. In such engines the fuel pumps have to inject a comparatively high amount of fuel within a short period of time through a plunger or piston having a comparatively large crosssectional area and reciprocated at high speed. Such pumps when they are required to deliver fuel under high mean pressure at a reduced rotational speed tend to cause inadmissibly high combustion pressures to be built up in the engine cylinders.

While this drawback may be averted by providing an injection timing adjustment involving means for varying the clearance between the cam and roller of the pump, this remedy in turn leads to other difiiculties: thus, in high speed engines, each time the cam is engaged by the roller animpact occurs, so that high speed operation is unsatisfactory, and the stresses required to vary the clearance between the cam and its follower roller are considerable.

On the other hand, in fuel pumps of the type provided with intake and exhaust valves, it is possible to adjust the injection timing by adjusting the exhaust valve for more or less early closure of this valve during the upward stroke of the pump piston. However, even though such adjustment does not require the exertion of considerable stresses, it does necessitate a complicated linkage with a large number of pivoted levers and is unsatisfactory for this reason.

In pumps wherein the adjustment of fuel delivery is accomplished by rotation of the pump piston alone, the former above-mentioned 'means may be applied, but in that case such a pump will be unsuitable for use in connection with a high-speed engine.

It is an object of this invention to provide an improved fuel-injection pump which overcomes the above drawbacks, and provides a simple-and efficient means for adjusting the injection timing.

Anobject is to adjust the injection timing in a diesel engine by setting the point, during the upward stroke of a piston in an injecting chamber communicating with an injection nozzle, at which said chamber will be sealed so that the piston will only then be effective to discharge fuel through said nozzle. Another object is to provide such an injection pump in which such setting is automatically obtained in correlation with the amount of fuel delivery into the engine. 7 Further objects will appear hereinafter;

'My-invention essentially comprises a fuel in- 2 jection pump having a pump cylinder chamber from which leads an injection nozzle, fuel intake means into and fuel exhaust means out of said chamber, a pump piston operating in said chamber and a valve so associated with said piston as to seal a duct within said piston only from a predetermined set point during its upward'stroke, said valve being then movable with said piston 'while remaining in sealing engagement with said communication from said chamber to said fuel exhaust means so that the piston will be ineffective to discharge fuel through said injection nozzle so long as the piston has not reached said predetermined set point of its upward stroke. The predetermined vertical setting of the valve in relation to the lower dead centre position of said piston, is in a preferred embodiment of the invention obtained by providing a valve shank extending axially through the piston and slidable therein, said shank projecting beyond the lower end of the piston and bearing upon an adjustable member through which the lowermost position of the valve head within the chamber above the top of the piston when in its lower dead centre position may be'varied.

In the accompanying drawings:

Fig. 1 is a view in axial cross-section of a fuelinjection pump according to the invention, and

Fig. 2 is a fragmentary view in section on the line II-II of Fig. 1.

As shown, an improved fuel-injection pump comprises a main pump body I in which a pump piston 2 is slidable. The pump body or cylinder l is formed near its top with two portsor ducts 3 and .4, the port 4 serving for the intake and the port 3 for the exhaust of fuel. An injection chamber 5 is defined in the cylinder I above the top of the piston 2- and an injection nozzle or jet 6 is fitted in the top of the pump body and is sup plied by the fuel under pressure built up within the chamber 5. A liner 1 is interposed between when seated on the top of the piston 2, seals the communication between the bore H and the chamber 5. The valve head [2 is connected with a valve shank I3 slidable in the piston bore I l and an annular recess 28 is formed in the valve shank l3, to provide communication from the intake port 4 to the injection chamber 5. Side "ducts or ports Ill are" formed in the piston 2" to gine cylinder.

register with the intake duct 4 and the ducts 8, 9 in the liner.

The valve shank l3 extends all the way down through the piston 2 and projects therefrom at its lower end, and. adjusting means are provided at said lower end to modify the initial vertical setting of the valve assembly l2-l3 with respect to the pump body. Said adjusting means in the example illustrated are formed as follows: the lower end of the valve shank l3 bears on an inclined element 14 seated on an inclined ramp l6 formed in a member l which is adjustably slidable transversely of the shank l3 in a transverse recess ll formed in an extension of the pump body or casing. The member I! is formed with rack teeth at I8 meshing with a pinion l9 rotatable by suitable means (not shown) from outside the pump.

Reciprocation of the pump piston 2 is accomplished as follows: the lower part of the pump body recess is enlarged as shown and has a bushing 24 slidable in it. The bushing 24 has a bottom extension, 23 integral therewith, which is recessed in order to accommodate the valve adjusting or setting members |4l5 previously described (see Fig. 2). The bottom end of the projection 23 is engaged by the top surface of an actuating piston member 22 slidable in a suitable bore formed at the bottom of the pump and reciprocated by a cam 20 engaging a follower roller 2| of the actuating piston 22.

The pump piston 2 rests on the top surface of the bottom of the bushing 24 through a base flange 26 of the piston 2 and a retaining ring 25 is pressed down over the piston flange 26 and the bottom of bushing 24 by a spring 21 acting between said ring and the top of the enlarged The above-described injection pump assembly operates as follows: the valve setting is first adjusted by rotating the pinion l9 which acts through the rackteeth l8 to position the member [5 in its recess I! in such a way that the inclined element l4 will impart a desired vertical setting to the valve assembly l3l2 relatively to the pump body I. When the cam 20 is rotated, the bushing 21 is reciprocated in its bore through the above-described set of associated parts 21-22-23 transmitting the drive from cam 20 to bushing 24. The pump piston 2 is similarly reciprocate'd being positively actuated in its upward stroke by the action of the cam 20 against the spring 2'! and returning on its downward stroke by the urge of this spring.

As the piston 2 starts rising from its lower dead centre position (substantially that shown in Fig. 1) the valve head I2 is first open because of the initial vertical setting imparted to the valve shank [3 in the previously described way; accordingly, the pressure of the fuel admitted through the intake port 4 cannot build up within the injection chamber 5 and no injection occurs through the injection nozzle 6 into the en- At a predetermined point of its upward movement however, as fixed by the valve setting, the top of the piston 2 reaches the valve head and henceforward carries the valve assembly l2-|3 with it on its upward stroke; thus fuel is trapped in the chamber 6, and injection accordingly commences.

While the means for rotating the pinion l9 and thus adjusting the injection timing have not been shown in the drawings, it is to be understood that any suitable manual or automatic means may be provided for this purpose. According to feature of the invention, these means may be correlated with the amount of fuel introduced into the chamber 5 at each reciprocation of the pump piston in such a manner that the injection lag will at all times be regulated as a function of the fuel delivery into the engine and/or with the speed of the engine.

It will be seen that the above arrangement provides a very simple and efficient type of injection timing adjustment. The seal of the valve has only to withstand the moderate pressure in the fuel intake pipe. Furthermore, the timing adjustment system of the invention eliminates the need of means for acting on the cam setting, as in prior systems, thus doing away with the complications and want of accuracy attendant to such constructions.

It should be understood that many alterations and changes may be made in the constructional details of the specific embodiment of the invention illustrated and described without departing from the scope of the invention as defined in the ensuing claims.

What I claim is:

1. In a fuel injection pump in combination a pump bodyhaving a pump cylinder chamber therein, a pump piston reciprocable in said cylinder, an injection nozzle leading from the top of said chamber, fuel-intake means into and fuel exhaust means out of said chamber, an axial bore through said piston opening into said chamber at the top of said piston, a valve having a valve head in said chamber above said piston and adapted to seal said bore, and a stem. slidably extending through said bore, and adapted to lift said valve above said bore for a predetermined lowermost position of said piston, said valve head when spaced above the top of said bore providing communication from said chamber to said fuel-inlet means, and when moving with said piston in sealed engagement with said bore sealin said chamber, bearing means provided for and connected to the lower end of said stem below said piston determining the vertical position of the valve head in said chamber, and means for adjusting the height of said bearing means, a camshaft, a cam fixedly set on said camshaft, thrust transmitting means from said cam to the bottom end of said piston and spring means associated with said piston to urge the piston in opposition to the thrust of the cam.

2. Fuel-injection pump as in claim 1 wherein said thrust-transmitting means comprise a lower piston slidable in said pump body and follower means on said lower piston engaged by said cam, and a recessed pusher part actuated by the top of said lower piston and actuating the bottom of said pump piston, said bearing means and height-adjustin means extending freely through the recess in said pusher.

3. In a fuel injection pump in combination a body defining a cylinder therein, a piston reciprocating in said cylinder, an injection chamber formed between said piston and the upper part of said cylinder, an injection nozzle leading from said chamber, lateral fuel inlet means in said cylinder and piston, a central hole in said piston communicating with said fuel outlet means and said injection chamber, a stem located in said hole, valve means at the upper part of said piston adapted to close said hole and to be lifted by said stem for a predetermined lowermost position of said piston, adjustable setting means for said stem remaining always in contact therewith aq'zaeoa and permitting of determining the initial position of said valve means and varying the point in the upward stroke of the piston at which said valve starts moving with and sealing the hole in said piston, thereby performing the injection, said settin means being immovable in the vertical direction upon the determination of the desired adjustment, and control means for causing the continuous reciprocation of said piston in accordance with the operation of the engine fed by said pump.

4. A pump according to claim 3 wherein said control means consist of cam means actuated by the usual pistons of the engine fed by the pumps and of piston means actuated by said cam means,

resilient means being provided for urging said' piston means against the action of said cam, said piston means being operatively connected with the said reciprocating piston, and further bearing means for the lower end of said stem below said piston means determining the vertical position or said valve means within said chamber, and means for adjusting the height of said hearing means for adjusting said vertical position of the valve.

5. A pump according to claim 4 wherein fuel outlet means are provided in said cylinder and adapted to be closed by said reciprocating piston.

6. Fuel-injection pump as in claim 5, wherein said bearing means for the lower end of said stem comprises an incline, and means for adjustably positioning said incline in a direction normal to the valve-shank for varying the efiective height of said bearing means.

7. Fuel-injection pump as in claim 6, wherein said bearing means comprises a member slidable in a direction normal to said stem, an incline on said member engaging the lower end of said stem, rackteeth on said member, and an adjusting pinion meshing with said rackteeth.

GUSTAV PIELSTICK.

Country Date Great Britain 1935 Number 

